Non-aqueous electrolyte secondary batteries have become increasingly important as, for example, power supplies loaded on electrically-driven vehicles, or as power sources loaded on PCs, mobile phones and other electric products, etc. In particular, lightweight lithium-ion secondary batteries with high energy densities are expected to be preferably used as high-power power supplies to be loaded on vehicles. Technical literatures relating to non-aqueous electrolyte secondary batteries include Patent Documents 1 to 3.
A non-aqueous electrolyte secondary battery may be charged as needed; however, overcharging might elevate the temperature. Patent Document 1 teaches to place a conductive intermediate layer that turns highly resistive when overcharged between a positive current collector and an active material-containing layer (or an active material layer hereinafter) in a lithium-ion secondary battery. According to this lithium-ion secondary battery, when overcharged, the resistance of the conductive intermediate layer increases, thereby reducing or shutting off the electric current flow. Thus, further temperature elevation is stopped in the lithium-ion secondary battery.